Spanning Tree Protocol, defined in IEEE 802.1d, used to eliminate redundant data paths and to increase
network efficiency. STP allows a network to have a topology that contains physical loops; it operates in
bridges and switches. STP opens certain paths to create a tree topology, thereby preventing packets
from looping endlessly on the network. To establish path redundancy, STP creates a tree that spans all
of the switches in an extended network, forcing redundant paths into a standby, or blocked, state.
STP allows only one active path at a time between any two network devices (this prevents the loops)
but establishes the redundant links as a backup if the initial link should fail. If STP costs change, or if one
network segment in the STP becomes unreachable, the spanning tree algorithm reconfigures the STP
topology and re-establishes the link by activating the standby path.
STPD
Spanning Tree Domain is an
instance that contains one or more
s. The switch can run multiple STPDs, and each STPD has its own root bridge and active
path. In the Extreme Networks implementation of STPD, each domain has a carrier VLAN (for carrying
STP information) and one or more protected VLANs (for carrying the data).
stub area
OSPF (Open Shortest Path First)
, a stub area is connected to only one other area (which can be the
backbone area). External route information is not distributed to stub areas.
superloop
EAPS (Extreme Automatic Protection Switching)
, a superloop occurs if the common link between two
EAPS domains goes down and the master nodes of both domains enter the failed state putting their
respective secondary ports into the forwarding state. If there is a data VLAN spanning both EAPS
domains, this action forms a loop between the EAPS domains.
SVL
In Shared VLAN Learning, two or more VLANs are grouped to share common source address
information in the MAC table. The common entry in the MAC table is identified by a Filter ID (FID). SVL
is useful for configuration of more complex, asymmetrical cross-VLAN traffic patterns, like E-TREE
(Rooted-Multipoint) and Multi-netted Server. The alternative VLAN learning mode is
. The default VLAN learning mode is IVL. Not all switches support SVL.
Syslog
A protocol used for the transmission of event notification messages across networks, originally
developed on the University of California Berkeley Software Distribution (BSD) TCP/IP system
implementations, and now embedded in many other operating systems and networked devices. A
device generates a messages, a relay receives and forwards the messages, and a collector (a syslog
server) receives the messages without relaying them.
Syslog uses the
as its underlying transport layer mechanism. The UDP
port that has been assigned to syslog is 514. (RFC 3164)
Terminal Access Controller Access Control System, often run on UNIX systems,provides access control
for routers, network access servers, and other networked computing devices via one or more
centralized servers. provides separate authentication, authorization, and accounting services.
User passwords are administered in a central database rather than in individual routers, providing easily
scalable network security solutions.
Glossary
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